1. Technical Field
The invention relates to a device for reading and/or writing information from/onto an optical information carrier, comprising                read means including imaging means for imaging a radiation beam so as to form a scanning spot by means of which the information carrier is scanned, and including detection means for generating a read signal which is indicative of the intensity of the radiation reflected from the information carrier at the location of the scanning spot,        which device has an information transfer mode, in which the scanning spot is moved in a first direction with respect to the information carrier,        which device has a displacement mode, in which the scanning spot is moved in a second direction transverse to the first direction,        control means for controlling the imaging means in response to a measurement signal which is indicative of the degree of focusing of the radiation beam at the location of the scanning spot, which control means include sample and hold means for sampling and holding the measurement signal in response to a sample signal.        
2. Related Art
From U.S. Pat. No. 5,245,598 a device is known which is suitable for scanning a magneto-optical disc-shaped information carrier. In the information carrier described therein the information is recorded in mutually concentric tracks which are separated by grooves. The information is recorded by forming magnetic patterns in the information carrier. The information is read by focusing a radiation beam is focused onto the information carrier and by measuring the polarization of the beam reflected from the location of the scanning spot thus formed. The scanning spot is then moved in a first direction, i.e. along the tracks. With the aid of detectors a focus error signal is derived from the reflected radiation. A sample and hold circuit generates a sampled focus error signal from the focus error signal. In response thereto a control system generates a control signal for focusing the beam. In a displacement mode of the device the sample and hold circuit is controlled by a tracking error signal, the focus error signal being sampled if the scanning spot is incident on a track and is maintained constant if the scanning spot is incident on a groove. According to said document the focus servo mechanism is preferably in a continuous sample mode during scanning of the information carrier. The measures taken in the known device suppress radial to vertical crosstalk (RV crosstalk) during a radial movement of the scanning spot on a magneto-optical information carrier as described above. However, the known measures do not suppress RV crosstalk which occurs in optical information carriers which store the information in the form of differences in level.